This invention concerns wastewater treatment plants, particularly clarifiers, and is directed to an improved clarifier launder construction that eliminates algae buildup and the need for algae sweeps, launder covers or frequent cleaning.
Clarifier launders typically are formed by a shelf of concrete, L-shaped in cross section and integral with the wall, on the inside or the outside of the clarifier wall. They can also be of other materials such as steel or FRP (fiberglass reinforced plastic). If inside, the conventional launder provides with its vertical leg a weir for overflow of effluent liquid into the launder with a weir plate attached to the top of the vertical leg. In an external concrete launder the top edge of the clarifier with weir plate attached provides the overflow weir.
Algae growth is a recurrent problem in conventional clarifier effluent launders. The launders are exposed to daylight, promoting algae growth, and must be cleaned frequently to remove the algae growth. Sometimes effluent launder algae sweeps have been installed, at significant capital and operational costs. Without these sweeps, plant operators must frequently clean the launders. In some cases effluent launder covers have been used to eliminate light and prevent algae growth.
The following documents have some relevance to the current invention: U.S. Pat. Nos. 8,220,644, 8,083,075, 7,416,662, 7,243,802, 6,712,222, 6,193,888, 5,597,483, 5,252,205, 5,277,077, 4,059,529 and 4,009,106, U.S. Pub. No. 2012/0248036 and British Patent No. GB 2115304. Of these references, U.S. Pat. No. 8,220,644, shows a somewhat typical inboard launder construction with density current baffle and scum baffle.